Mitt Romney picks up some ground on his two main rivals in the latest FOX News poll as the Granite State’s first-in-the-nation primary looms closer — at just over three weeks away.

The poll shows that John McCain and Rudy Giuliani still are capable of making the race closer, but Romney holds the allegiance of a full one-third of likely Republican primary voters (33 percent) — up from 29 percent in the FOX News poll conducted at the end of November.

McCain draws one in five voters (20 percent), close to the 21 percent he claimed in the previous poll. Giuliani garners 16 percent — down 3 points from the 19 percent he held at the end of last month. Much of the movement in the race may be due to the drop in undecided sentiment, which went from 14 percent in November to 8 percent in this new poll.

Opinion Dynamics Corp. conducted the telephone poll of 500 likely Republican primary voters in New Hampshire for FOX News from Dec. 11 to Dec. 13. The poll has a 4-point error margin.

Click here to view full results of the poll (pdf).

A second tier of candidates was comprised of Mike Huckabee (11 percent) and Ron Paul (8 percent), with Fred Thompson, Tom Tancredo and Duncan Hunter trailing far behind in the low single digits or less.

The poll also finds that Romney supporters are more certain of their vote (60 percent) than are supporters of Giuliani (55 percent) or McCain (54 percent).

Moreover, Romney voters are more likely to think their candidate can win the November 2008 general election (63 percent) than are Giuliani supporters (60 percent) or McCain supporters (53 percent). This last result represents a shift in sentiment from the November poll, when Giuliani voters clearly were more confident than others on this score.

Among the top three contenders, Romney voters also are the most enthusiastic about their choice (84 percent), followed by Giuliani voters (81 percent) and McCain voters (75 percent).

The share of likely Republican primary voters who would be very satisfied with a Romney nomination stands at 40 percent, while 30 percent would feel the same way about McCain being the GOP standard-bearer and 27 percent would be very satisfied with Giuliani at the top of the ticket. Just under one in five (19 percent) would be very satisfied with a Huckabee nomination.

The poll shows a plurality of likely Republican primary voters continues to think the economy is the single most important issue in the election (21 percent, the same level as in November).

Immigration, at 16 percent, comes in second on the important-issues list, followed by the war in Iraq (14 percent), homeland security (12 percent), social issues such as abortion and gay marriage (11 percent) and health care (10). Taxes (7 percent) and education issues (2 percent) lag far behind.

The poll finds that "standing up for one’s beliefs" (53 percent) is a more important candidate attribute to likely Republican primary voters than is experience (21 percent) or being a true conservative (14 percent).

Just over half of all likely Republican voters (54 percent) approve of the job George W. Bush is doing as president, with about four in 10 (41 percent) disapproving of his job performance.

Among an array of celebrities who have endorsed candidates in the New Hampshire primary, Boston Red Sox pitcher Curt Schilling is the most impactful — with 14 percent of likely Republican primary voters saying he would have the most influence on their vote. Schilling endorsed John McCain.

Next most influential is Oprah Winfrey (7 percent) — despite her backing of Democratic contender Barack Obama. Actor Chuck Norris’ endorsement of Mike Huckabee comes in third at 6 percent, followed by Barbra Streisand’s endorsement of Hillary Clinton at 1 percent.

Nearly half of all likely Republican primary voters say they are pro-life (49 percent), with just under four in 10 saying they are pro-choice (38 percent). "Pro-life" voters give Romney a commanding 23-point lead over McCain (39 percent to 16 percent), with Huckabee claiming 14 percent of these and Giuliani getting 11 percent.